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So, let us talk plainly. You absolutely, definitely, positively should be using TLS / HTTPS encryption on the sites that you run.

HTTPS provides encryption, meaning that anyone watching the connection (and yes, people do care, and are absolutely watching), will have a harder time trying to extract content information about the connection. This is important, because it stops your credit card being read as it makes its way to Amazon’s servers, or your password being read when you log into your email.

When I advise my clients on infrastructure, these days I recommend that all pages on a website, regardless of that page’s contents, should be served over HTTPS. The primary reason being a feature of an encrypted connection which I don’t think gets underlined enough.

Tamper resistant web

When you serve content over HTTPS, it is significantly harder to modify. Or, to put it another way, when you serve pages unencrypted, you have absolutely no guarantee that the page your server sends is going to be the page that your visitor receives!

If an attacker controls a link in the chain of computers between you and the site you’re visiting it is trivial to modify requests to and from a visitor and the server. A slightly more sophisticated attacker can perform these attacks without the need to control a link in the chain, a so called “Man on the side” attack – more technically complex, but still relatively trivial with sufficient budget, and has been widely automated by state actors and criminal gangs.

The capabilities these sorts of attacks give someone are limited only by budget and imagination. On a sliding scale of evil, possibly the least evil use we’ve seen in the wild is probably the advertising injection attack used by certainISPs and Airplane/hotel wifi providers, but could easily extend to attacks designed to actively compromise your security.

Consider this example of an attack exploiting a common configuration:

A web application is installed on a server, and the site is available by visiting both HTTP and HTTPS endpoints. That is to say, if you visited both http://foo.com and https://foo.com, you’d get the same page being served.

Login details are sent using a POST form, but because the developers aren’t complete idiots they send these over HTTPS.

Seems reasonable, and I used to do this myself without seeing anything wrong with it.

However, consider what an attacker could do in this situation if the page serving the form is unencrypted. It would, for example, be a relatively trivial matter, once the infrastructure is in place, to simply rewrite “https://” to “http://”, meaning your login details would be sent unencrypted. Even if the server was configured to only accept login details on a secure connection (another fairly common practice), this attack would still work since the POST will still go ahead. A really sophisticated attacker could intercept the returning error page, and replace it with something innocuous, meaning your visitor would be non the wiser.

It gets worse of course, since as we have learnt from the Snowden disclosures, security agencies around the world will often illegally conscript unencrypted web pages to perform automated attacks on anyone they view as a target (which, as we’ve also learnt from the Snowden disclosures, includes just about everybody, including system administrators, software developers and even people who have visited CNN.com).

Lets Encrypt!

Encrypting your website is fairly straightforward, certainly when compared to the amount of work it took to deploy your web app in the first place. Plus, with the new Lets Encrypt project launching soon, it’s about to get a whole lot easier.

You’ll need to make sure you test those configurations regularly, since configuration recommendations change from time to time, and most shared hosts & default server configurations often leave a lot to be desired.

However, I assert that it is worth the extra effort.

By enabling HTTPS on the entire site, you’ll make it much much harder for an attacker to compromise your visitor’s privacy and security (I say harder, not impossible. There are still attacks that can be performed, especially if the attacker has root certificate access for certificates trusted by the computer you’re using… so be careful doing internet banking on a corporate network, or in China).

You also add to the herd immunity to your fellow internet users, normalising encrypted traffic and limiting the attack surface for mass surveillance and mass packet injection.

After finding out the day before that GCHQ had spied on lawyers, we now find out that GCHQ and the NSA conspired to steal the encryption keys to pretty much every sim card in the world, meaning that they can easily break the (admittedly weak) encryption used to protect your phonecalls and text messages.

Personally, I’m not terribly concerned about this, because the idea that your mobile phone is insecure is hardly news. What is of concern to me, is how they went about getting those keys.

It seems that in order to get these keys, the intelligence agencies hunted down and placed under invasive surveillance ordinary innocent people, who just happened to be employed by or have dealings with the companies they were interested in.

The full capabilities of the global surveillance architecture they command was deployed against entirely unremarkable and innocent individuals. People like you and me, who’s entire private lives were sifted through, just in case they exposed some information that could be used against the companies which they worked.

Nothing to hide, nothing to fear

If there is a silver lining in all this, with any luck it will go some way towards shattering the idea that because you have nothing to hide, you have nothing to fear.

This is, primarily, a coping strategy. It’s a lie people tell themselves so they can avoid confronting an awkward or terrifying fact, a bit like saying climate change isn’t real, or that smoking won’t kill me.

Generally, it is taken to mean that you’ve done nothing wrong, i.e. illegal (and of course, that’s not what privacy is about, and what you consider being “wrong” has typically not been the same as what those in power consider “wrong”).

Fundamentally, it misses the point that you don’t get to decide what others are going to find interesting, or suspect you of knowing. In this instance, innocent people had their privacy invaded purely because they had suspected access to information that the intelligence agencies found interesting. This is something that, were I to do something similar, I’d go to jail for a very long time.

Now consider that one of the NSA’s core missions is to advance US economic interests, spying on Brazilian oil companies and European trade negotiations, etc. If I worked at a competitor of a US company, I’d be very careful what I said in any insecure form of communication.

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When building personal or internal projects, it is common practice to use self signed certificates in order to enable HTTPS support.

Self signed certificates, as the name implies, are certificates which you generate yourself. They are generally frowned on from a security point of view, since although they make encryption possible, as they are not signed by a recognised authority, they make no guarantees about trust.

This means that, at the very least, you’ll get a warning in your browser. Worse, it becomes very easy for an attacker to MITM your connection, since both situations will trigger a warning, unless you manually compare key signatures, you’ll never know.

The good news is that, if the only clients that ever connect to your service are under your control (your own custom client, or a browser on your computers in your office, etc), you can use self signed certificates safely by becoming your own certificate authority.

… So here’s how (mainly for my own reference).

Becoming your own certificate authority

The first step is to generate your own master key and certificate that you’ll use to sign your keys.

Start, by generating your root key. It is very important that you keep this safe as anyone who somehow gets a copy of it could create certificates signed as you!

openssl genrsa -out root.key 4096

Next, generate your master certificate using this key

openssl req -x509 -new -nodes -key root.key -days 1825 -out root.pem

Once you’ve generated this certificate, you need to install it on your clients. How this is done varies from client to client, but most browsers have an option (usually in the “advanced” or “security” section) to install a certificate provider. Have a google for “YOUR CLIENT” and “installing certificate” will usually get you somewhere.

On iOS devices the process is simply a matter of emailing the .pem to yourself and clicking on it, and the device will guide you through installation. This will make it available to Safari, but irritatingly there seems to be no way to install certificates for Chrome on iOS.

To update linux command line apps (incuding curl), copy and rename the .pem to /usr/local/share/ca-certificates and then run update-ca-certificates as root.

Generate your server certificates

Once you’ve installed your certificate authority key on the various computers and devices under your control, you are free to generate as many self signed certificates as you wish. Once these certificates are signed by your certificate authority, they will be accepted as legit by all the computers that you’ve installed your root.pem on.

This will provide not only encryption, but also trust, providing protection against eavesdropping and spoofing.